An orthopaedic surgical system (10) includes a sensor module(12) for determining the joint force of a patients knee joint and an adaptor (502) for coupling various tibial trialing components (504, 505, 506) to the sensor module. The sensor module includes a tibial paddle (34) to which the adaptor is configured to couple. The adaptor and tibial paddle include structures that control the orientation at which the adaptor is attachable to the tibial paddle. Tibial trialing components can be positioned over the adaptor in a mobile orientation that facilitates rotation of the tibial trialing component relative to the tibial paddle or a fixed orientation that restricts the rotation of the tibial trialing component.
